1. Field of the Invention
The present invention relates to the control of airborne contamination in a machine and, more particularly, to the control of airborne contaminants so that certain components in a machine are not contaminated by contaminants generated by other components of the same machine.
2. Prior Art
Electrical machines such as copiers, tend to generate and release undesirable airborne elements. These elements tend to contaminate machine components and the atmosphere. It is believed that the airborne elements are released from electrical components. The release is believed to be more pronounced when the temperature of the components is elevated.
Because some types of airborne elements tend to be injurious to one's health if inhaled, the prior art tends to control entry of the airborne elements into the atmosphere. Ozone is one of the airborne elements which is hazardous to health. It is believed that this hazardous gas is generated from high voltage and heat generating components and heat generating processes. The prior art attempts to control ozone by limiting the percentage and/or concentration of ozone emitted from a machine into the atmosphere. This is done by placing a filter which absorbs and/or decomposes ozone from the air prior to exhausting it into the atmosphere.
By way of example, U.S. Pat. No. 4,202,618 describes an apparatus for controlling the amount of ozone which is outputted from a copier into the atmosphere. The ozone is generated by a flash lamp which fuses microscopic toner onto a copy sheet. A first cooling air passage is disposed about the flash lamp. The air passage carries a cooling airstream of low volumetric flow rate and interconnects the flash lamp with the ambient atmosphere. An activated carbon filter is placed in the first cooling air passage downstream from the flash lamp. A second cooling airstream of high volumetric flow rate is disposed so that air exiting from the filter mixes with the air in the second cooling stream. As such, the air carrying the ozone is diluted prior to actual discharge from the copier.
IBM Technical Disclosure Bulletin Vol. 23, No. 12, May 1981 (pages 5620-5621) shows an ozone-removing charcoal filter mounted inside a photoconductor drum. Ozone which is generated from the photoconductor is extracted by creating an airflow through the charcoal filter.
IBM Technical Disclosure Bulletin Vol. 24, No. 6, November 1981 (page 2816) describes the use of an expanded metal foam to getter unwanted gases from the inert gases used in vacuum deposition processes.
European patent application, Ser. No. 81301706.8, filed Apr. 16, 1981, published Oct. 21, 1981 and Xerox Disclosure Journal Vol. 6. No. 5, September/October 1981 (pg. 217) describe specific types of ozone filters, all of which are suitable to filter ozone from an airstream.
Although the prior art attempts to control the discharge of ozone into the ambient atmosphere, it does not address the problem of airborne elements contaminating other components of a machine. It is this type of problem that the present invention addresses. For purposes of discussion, it will be assumed that the machine is a copier. One type of airborne contaminant is dioctyl phthalate, hereinafter called DOP. It is believed that DOP is present in most types of soft vinyl wire insulation. At elevated temperatures, DOP can be expelled from those parts. The DOP moves with the convective or driven airflow to condense on cooler components of the machine.
In the case of a copier, the DOP condenses on the photoconductor and forms a source of contamination. The condensation usually occurs in the region of the photoconductor relative to the transfer/paper separator corona. The deposit plasticizes the toner and causes it to adhere more tenaciously to the photoconductor. As such, cleaning of the toner from the photoconductor is much more difficult. Moreover, in those copiers which use a cleaning blade to remove residual toner, the toner forms a line of deposit on the photoconductor. The line runs parallel to the blade. The build-up of toner on the photoconductor reduces the quality of the copies.
It is worthwhile noting that the invention to be described hereinafter will protect some machine components from plasticizer. The plasticizer is usually generated by other machine components. DOP is only one type of plasticizer.